The microstructures of exoskeletons from Homarus americanus (American lobster) and Callinectes sapidus (Atlantic blue crab) were investigated to elucidate the mechanical behavior of such biological composites. Image analyses of the cross-sectioned exoskeletons showed that the two species each have three well-defined regions across the cuticle thickness where the two innermost regions (exocuticle and endocuticle) are load bearing. These regions consist of mineralized chitin fibers aligned in layers, where a gradual rotation of the fiber orientation of the layers results in repeating stacks. The exocuticle and endocuticle of the two species have similar morphology, but different thicknesses, number of layers, and number of stacks. Mechanics-based analyses showed that the morphology of the layered structure corresponds to a nearly isotropic structure. The cuticles are inter-stitched with pore canal fibers, running transversely to the layered structure. Mechanics-based analyses suggested that the pore canal fibers increase the interlaminar strength of the exoskeleton.

Accurate mechanical property measurement of films on substrates by instrumented indentation requires a solution describing the effective modulus of the film/substrate system. Here, a first-order elastic perturbation solution for spherical punch indentation on a film/substrate system is presented. Finite element method (FEM) simulations were conducted for comparison with the analytic solution. FEM results indicate that the new solution is valid for a practical range of modulus mismatch, especially for a stiff film on a compliant substrate. It also shows that effective modulus curves for the spherical punch deviates from those of the flat punch when the thickness is comparable to contact size.

A glass-ceramic (GC0) with nominal composition of 51.2% CaO–12.1% MgO–36.7% SiO2 (wt%) was synthesized. Then multiphase glass-ceramics of MGC1 and MGC2 were obtained by adding 1 and 2 wt% B2O3 to GC0 followed by thermal treatment. The bending strength of MGC1 was the highest, about 89.46 MPa, and the coefficient of thermal expansion was 10.67 × 10−6 °C−1, closer to that of Ti–6Al–4V alloy (10.03 × 10−6 °C−1). X-ray diffraction analysis confirmed that MGC1 was predominantly composed of akermanite, merwinite, and small amounts of dicalcium silicate crystalline phases. The bioactivity and cytocompatibility in vitro of MGC1 were detected by investigating the bonelike apatite-formation ability in simulated body fluid (SBF) and osteoblast morphology and viability. The results showed that MGC1 possessed bonelike apatite-formation ability in SBF and could release ionic products to significantly stimulate cell growth and viability. Furthermore, osteoblasts adhered and spread well on MGC1, indicating good bioactivity and potential cytocompatibility.

Three sets of original dynamics model parameters for MgO–Al2O3–SiO2 (MAS) system were reported for the first time in this paper; moreover, a new parameter optimization standard was put forward to study three different molecular dynamic models of MAS glass-ceramics. The limitations of the conventional parameter optimization methods were also studied. The results indicate: (i) Born-Mayer-Huggins (BMH) model can be only used to simulate amorphous MAS systems. Furthermore, both static optimization and a dynamics test are necessary; (ii) for structure optimization or macroproperties calculation, high accuracy has been achieved relative to the experimental results by using the core-shell (CS) model; (iii) partialQ model computes at a high speed, about twelve times that of the CS model; (iv) for a bulk system, the partialQ model can be first used to obtain an initial structure rapidly, followed by the CS model for high accuracy calculation. In this way, both accuracy and efficiency are achieved. When the model was used to simulate the cordierite crystal and the amorphous in the cordierite glass-ceramic, the results were consistent with the experiments and the structure data from the ab initio calculation. Simulations on amorphous structures in the cordierite glass-ceramic with various compositions displayed that the bond length or coordination numbers (CN) of Si–O and Al–O remained the same with increasing content of MgO, suggesting no change in the tetrahedral configuration of short-range structure. Although the bond length of Mg–O stays almost the same with the increasing content of MgO, the coordination number increases to a certain extent, and the content of O-bridge in SiO2 glass drops from 100%–60% in pyrope glass.

In complex transition-metal oxides, the interactions between the electronic spins, charges, and orbitals produce a rich variety of electronic phases. The competition and/or cooperation among these correlated-electron phases can lead to the emergence of surprising electronic phenomena and functionalities and form the basis for a new type of electronics.

Direct current (dc) electrodeposition was used to co-deposit cobalt and antimony in citric-based solutions. Growth behavior of Co–Sb alloy thin films was systematically studied under various deposition conditions. Effects of deposition parameters (i.e., deposition potential, cobalt sulfate concentration, and pH value) on the microstructure, chemical, and phase composition of the deposited materials were also studied and are discussed in detail.

The effect of microstructural inhomogeneities with different length scale on the plasticity of (Ti45Zr16Be20Cu10Ni9)100–xTax (x = 0, 5, and 10) bulk glassy alloys has been studied. The formation of specific heterogeneous microstructures with a different type of structural inhomogeneity, i.e., short-/medium-range ordered clusters or micrometer-scale ductile dendrites combined with a glassy matrix, evolved by appropriately tuning the alloy chemistry, improves the room temperature plasticity up to ∼12.5% and ∼15%, respectively. The pronouncedly enhanced plasticity is mainly attributed to the retardation of shear localization and multiplication of shear bands by controlling the plastic and failure instabilities otherwise responsible for premature failure.

A new type of composite metal–nanoparticle coating that significantly reduces the friction force of various surfaces, particularly archwires in orthodontic applications, is demonstrated. The coating is based on electrodeposited Ni film impregnated with inorganic fullerene-like nanospheres of tungsten disulphide. The first encouraging tests have shown reduction of up to 60% of the friction force between coated rectangular archwires and self-ligating brackets in comparison with uncoated archwires. The coating not only significantly reduces friction of commercial archwires but also maintains this low value of friction for the duration of the tests in comparison to archwires coated with nickel film without the nanoparticles. The coated surfaces of the wires were examined by scanning electron microscopy equipped with energy dispersive analyzer and by x-ray powder diffraction methods before and after the friction tests. Using these analyses, it was possible to qualitatively estimate the state of the Ni+IF-WS2 coating before and after the friction test compared to Ni coated wires without IF-WS2.

The nanostructure of Six(SiO2)1–x films deposited on quartz substrate, where x varies from 0 to 1, was determined by high-resolution transmission electron microscopy in the sample regions with x ≈ 0.1, 0.2, 0.5, and 0.75. In the Si0.5(SiO2)0.5 region, the formation of a Si nanocrystallite network was established. At high concentrations of Si nanocrystallites, nanotwins and stacking faults occurred in the crystallites. Large Si crystallites appeared at x ⩾ 0.5 in the quartz substrate under the interface, while the film presented nanopores over the interface. The mechanisms for the formation of the nanocrystallites were discussed and correlated with the film properties.

The dielectric anomalies and their structure dependence were evaluated and discussed in Sr4(LaxNd1-x)2Ti4Nb6O30 ceramics, together with the analysis of ultrasonic velocity shift and attenuation spectra in the low-temperature range. The room-temperature structure was confirmed as the tetragonal in space group P4bm for all compositions. One diffuse ferroelectric peak and three relaxor ferroelectric peaks corresponding to the commensurate/incommensurate modulation of oxygen octahedra, polar clusters of A-site ion ordering, and B-site ion ordering, respectively, were observed in the composition with x = 0.25. With decreasing the radius difference between A1- and A2-ions (increasing x), the dielectric relaxations, especially the one originating from the polar clusters of A-site ion ordering, tended to increase significantly and overlap the diffuse ferroelectric peak, which was completely overlapped for x ⩾ 0.75. This process just reflected the increased disordering degree of both A- and B-site ions, and the analysis of ultrasonic attenuation strongly supported the above conclusions on dielectric relaxations and their structural origins. The ultrasonic attenuation peak at approximately 100 K corresponded to the freezing process of the dielectric relaxations, and the fluctuation with composition of the ultrasonic attenuation peaks between 150 and 260 K suggested the possible structure variation.

Lead loss during processing of solution-derived Pb(Zr,Ti)O3 (PZT)-based thin-films can result in the formation of a Pb-deficient, nonferroelectric fluorite phase that is detrimental to dielectric properties. It has recently been shown that this nonferroelectric fluorite phase can be converted to the desired perovskite phase by postcrystallization treatment. Here, quantitative standard-based energy-dispersive x-ray spectrometry (EDS) in a scanning transmission electron microscope (STEM) is used to study cation distribution before and after this fluorite-to-perovskite transformation. Single-phase perovskite PbZr0.53Ti0.47O3 (PZT 53/47) and Pb0.88La0.12Zr0.68Ti0.29O3 (PLZT 12/70/30) specimens that underwent this treatment were found to be chemically indistinguishable from the perovskite present in the multiphase specimens prior to the fluorite-to-perovskite transformation. Significant Zr–Ti segregation is found in PLZT 12/70/30, but not in PZT 53/47. Slight La-segregation was seen in rapidly crystallized PLZT, but not in more slowly crystallized PLZT.

Two-dimensional electron gases (2DEGs) based on conventional semiconductors such as Si or GaAs have played a pivotal role in fundamental science and technology. The high mobilities achieved in 2DEGs enabled the discovery of the integer and fractional quantum Hall effects and are exploited in high-electron-mobility transistors. Recent work has shown that 2DEGs can also exist at oxide interfaces. These electron gases typically result from reconstruction of the complex electronic structure of the oxides, so that the electronic behavior of the interfaces can differ from the behavior of the bulk. Reports on magnetism and superconductivity in oxide 2DEGs illustrate their capability to encompass phenomena not shown by interfaces in conventional semiconductors. This article reviews the status and prospects of oxide 2DEGs.

High-temperature order–disorder transformations in R2T17 and R2T17-M-C intermetallics with R = Pr, Sm, Dy, Tb; T = Co, Fe; and M = Zr, Nb were studied utilizing time-resolved synchrotron x-ray diffraction at the Advanced Photon Source (APS) at the U.S. Department of Energy’s Argonne National Laboratory (Argonne, IL). High-energy synchrotron radiation provides intense, highly penetrating x-rays, which are ideal for in situ studies of phase transformations. Alloying additions are used to stabilize formation of metastable phases; their influence on order recovery was investigated. The experimental setup utilized Debye–Scherrer geometry; specimens were heated at a rate of 10 K/min. Full-profile diffraction patterns collected every 10 s were refined in sequence using the Rietveld method to track changes of lattice parameters and phase assemblages during heating. Sharp changes observed in the evolution of temperature-dependent lattice parameters suggested formation of ordered structure via nucleation and growth. Both 2-17 polymorphs co-existed in light and heavy rare-earth systems at high temperatures. The presence of alloying additions in the solid solution greatly influenced long-range order formation.

Magnetism in oxides was thought to be well-understood in terms of localized magnetic moments and double-exchange or superexchange rules. This understanding was shaken by the publication of an article in 2001 stating that thin films of anatase TiO2 with only 7 at.% Co substitution had a Curie point in excess of 400 K [Matsumoto et al., Science291, 854 (2001)]. Room-temperature ferromagnetism had previously been predicted for p-type ZnO with 5 at.% Mn [Dietl et al., Science287, 1019 (2000)]. A flood of reports of thin films and nanoparticles of new oxide “dilute magnetic semiconductors” (DMSs) followed, and high-temperature ferromagnetism has been reported for other systems with no 3dcations. The expectation that these materials would find applications in spintronics motivated research in this area. Unfortunately, the data are plagued by instability and a lack of reproducibility. In many cases, the ferromagnetism can be explained by uncontrolled secondary phases; it is absent in well-crystallized films and bulk material. However, it appears that some form of high-temperature ferromagnetism can result from defects present in the oxide films [Coey, Curr. Opin. Solid State Mater. Sci.10, 83 (2007); Chambers, Surf. Sci. Rep.61, 345 (2006)], although they are not DMSs as originally envisaged.